Prototype sub-wavelength structure anti-reflection coating on alumina filters for ground-based CMB telescopes
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arXiv
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| Main Authors: | , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866909612620382208 |
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| author | Aizawa, Kosuke Akizawa, Ryosuke Cray, Scott Hanany, Shaul Kawano, Shotaro Koch, Jürgen Konishi, Kuniaki Lam, Rex Matsumura, Tomotake Sakurai, Haruyuki Takaku, Ryota |
| author_facet | Aizawa, Kosuke Akizawa, Ryosuke Cray, Scott Hanany, Shaul Kawano, Shotaro Koch, Jürgen Konishi, Kuniaki Lam, Rex Matsumura, Tomotake Sakurai, Haruyuki Takaku, Ryota |
| contents | We present designs and fabrication of sub-wavelength anti-reflection (AR) structures on alumina for infrared absorptive filters with passbands near 30, 125, and 250 GHz. These bands are widely used by ground-based instruments measuring the cosmic microwave background radiation. The designs are tuned to provide reflectance of 2% or less for fractional bandwidths between 51% and 72%, with each of the three primary bands containing two sub-bands. We make the sub-wavelength structures (SWS), which resemble a two-dimensional array of pyramids, using laser ablation. We measure the shapes of the fabricated pyramids and show that for incidence angles up to 20 degrees the predicted in-band average reflectance is 2% or less, in agreement with the design. The band average instrumental polarization is less than $3\times 10^{-3}$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2505_11118 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Prototype sub-wavelength structure anti-reflection coating on alumina filters for ground-based CMB telescopes Aizawa, Kosuke Akizawa, Ryosuke Cray, Scott Hanany, Shaul Kawano, Shotaro Koch, Jürgen Konishi, Kuniaki Lam, Rex Matsumura, Tomotake Sakurai, Haruyuki Takaku, Ryota Instrumentation and Methods for Astrophysics Cosmology and Nongalactic Astrophysics We present designs and fabrication of sub-wavelength anti-reflection (AR) structures on alumina for infrared absorptive filters with passbands near 30, 125, and 250 GHz. These bands are widely used by ground-based instruments measuring the cosmic microwave background radiation. The designs are tuned to provide reflectance of 2% or less for fractional bandwidths between 51% and 72%, with each of the three primary bands containing two sub-bands. We make the sub-wavelength structures (SWS), which resemble a two-dimensional array of pyramids, using laser ablation. We measure the shapes of the fabricated pyramids and show that for incidence angles up to 20 degrees the predicted in-band average reflectance is 2% or less, in agreement with the design. The band average instrumental polarization is less than $3\times 10^{-3}$. |
| title | Prototype sub-wavelength structure anti-reflection coating on alumina filters for ground-based CMB telescopes |
| topic | Instrumentation and Methods for Astrophysics Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2505.11118 |